The value of 1.5 Tesla magnetic resonance imaging (MRI) in defining gliomas is well established, but does not necessarily identify the full extent of involvement by tumor cells, or markers for tumor grade such as neovascularity, pleomorphism, nuclear to cytoplasmic ratio, cell density and endothelial proliferation. Images acquired from normal volunteers with 8T ultra high field MRI (UHFMRI) system have a 4 fold increase in resolution versus typical 1.5 Tesla commercial clinical systems (i.e. General Electric Signa Horizon MRI System) and two-fold increase in signal to noise when compared to the few 4 Tesla research magnetic resonance systems operating at other research sites. This could be critical for enhancing the sensitivities of MR imaging to gliomas. SPECIFIC AlMS: (1) To determine if the improved spatial resolution and magnetic susceptibility-based vascular enhancement obtained with UHFMRI allows for the identification of abnormal vascularity in gliomas. (2) To determine whether areas of increased vascularity identified at 8T correspond to areas of increased vascularity on histopathologic analysis. (3) To determine whether areas of increased vascularity identified at 8T correspond to areas of perfusion one contrast enhanced 1.5 T MRI. A group of 80 patients with astrocytoma will undergo pre-operative high-resolution gradient echo imaging at 8T. Subsequently, these same patients will undergo contrast enhanced MRI and perfusion MRI at 1 .5T. Foci of increased vascularity will be identified on 81 images. Semi-quantitative grades for blood vessels will be made from the 1.5 and 8 T images by two reviewers. The high vessel density foci will then be biopsied using intra-operative stereotactic-guidance. The tissue will be histologically evaluated using vessel stains and a semi-quantitative vessel grading will be made. Correlation of the various vessel grades will be made between the histologic findings and the MR findings. Reliability will be measured on the basis of interobserver and intraobserver agreement. Secondary outcome measures will be used as pilot data in order to plan future investigations.